As fibers that are resistant to combustion when exposed to flame, and have no thermal fusibility, cotton and wool fibers treated with a flame-retarder, flame-retardant Vinylon (trademark) and flame-retardant rayon are known and supplied as a flame-retardant cloth-forming material to commercial markets. Those conventional flame-retardant fibers are disadvantageous in that said fibers sometimes do not necessarily have flame resistance or heat resistance sufficient to protect the wearer when exposed to temperatures of 200.degree. C. or more for an extended period.
The fabric made from the above-mentioned flame retarder-treated fibers essentially have no heat-setting properties. Therefore, a cloth made from the flame retarder-treated fiber is disadvantageous in that the trim appearance of the cloth is nullified by vanishing pleats or wrinkles forming thereon during wear, and thus the garment must be ironed after every wear. Wrinkles are also formed after laundering, thereby necessitating ironing before use if a trim appearance is required.
On the other hand, carbonized rayon fibers and polybenzimidazole fibers are known as fibers having excellent heat resistance and flame resistant, and are supplied for practical use as a material for flame resistant cloth. However, these fibers are poor in dyeability and a resultant cloth made from said fibers provides an unsatisfactory appearance, texture and mechanical strength, whereas the fibers have a high heat resistance and flame resistance. Accordingly, poly(metaphenyleneisophthalamide) fibers having excellent heat and flame resistance, mechanical strength sufficiently high when formed into a working cloth, and satisfactory dyeability in every color, are now widely used as a material for flame resistant cloth.
Nevertheless, the poly(metaphenyleneisophthalamide) fibers are essentially heat resistant fibers and thus have poor heat-setting properties. Thus, a fabric comprising, as the main component thereof, such fibers exhibits poor form-retaining properties and dimensional stability similar to those of a fabric made from cellulose fibers. Therefore, when a cloth sewn from the fabric is worn, pleats on the cloth vanish and wrinkles are formed, which degrade the appearance of the cloth. Therefore, the cloth must be ironed after every wear or laundered. However, since the functional properties, for example, heat resistance, flame resistance and flame retardance, of the poly(metaphenyleneisophthalamide) fibers are considered to be important, an elimination of the above-mentioned disadvantages, namely, low form-retaining properties and dimensional stability, of the fibers have not yet been considered.
On the other hand, polyester fibers have excellent heat-setting properties, and in a cloth made from the polyester fibers, pleats retain their form and wrinkles are not formed during wear. Also, the cloth is advantageous in that wrinkles do not form on the cloth after laundering, and thus is widely utilized as a wash-and-wear cloth.
In a fiber-blend fabric containing cellulose fibers, for example, cotton and rayon fibers, having no heat-setting properties, when the blending ratio of the polyester fibers to the cellulose fibers is adjusted to 65 weight%: 35 weight%, the resultant fabric exhibits relatively high form-retaining properties and dimensional stability and thus is widely and practically used.